1. Field of the Invention
The present invention relates to a video de-interlace apparatus and a method thereof. More particularly, the present invention relates to a video de-interlace apparatus based on film originated combing and a method thereof.
2. Description of Related Art
The speed of 24 fields per second (i.e. 3:2 film format) or 30 fields per second (i.e. 2:2 film format) is generally used for shooting a film. However, the video standard of TV is 50 fields per second or 60 fields per second, so when a film is played on TV, a frame has to be dismantled alternatively into two fields and a plurality of fields have to be additionally inserted to maintain the playing speed of the film. Such an operation is referred to as telecine, and the most popular telecine formats include 2:2 pull-down and 3:2 pull-down.
With NTSC video as example, which requires 60 fields per second, when the video is in 3:2 film format, which has only 24 frames per second, there are only 48 fields per second if these frames are directly divided into odd fields and even fields, as shown in FIG. 1A, a frame 11 has to be divided into an odd field O111 and an even field E111, and another frame 12 has to be divided into an odd field O121, an even field E122, and an odd field O123, and so on, to obtain 60 fields. The foregoing operation is referred to as 3:2 pull-down. FIG. 1B illustrates the conventional 2:2 pull-down. Since original 2:2 film format has 30 frames per second, so all the frames F01 are simply divided into odd fields O01 and even fields E01.
When a TV receives the video, it plays the fields one after another alternatively, thus, the fields have to be de-interlaced before being played so as to prevent combing problem caused by two different fields appearing in one image. FIG. 2 illustrates the combing caused when two different fields appear in one image. There are many ways for de-interlacing a video, generally speaking, if the video source is in film format, the best de-interlace method is to combine the two fields of a frame back into a frame to obtain the clearest image, and such an operation is referred to as weave, and the most popular weaving methods include inverse 2:2 pull-down and inverse 3:2 pull-down. FIGS. 3A and 3B respectively illustrate inverse 2:2 pull-down and inverse 3:2 pull-down.
Since a video may be originated from 2:2 pull-down, 3:2 pull-down, or a general video, the video has to be analyzed and determined before inverse telecine is performed to the video, so that whether a particular field should be weaved with a previous field or a next field, or a general de-interlace operation should be performed can be determined.